home backup power

In the science fiction television Stargate universe, a DHD (for Dial-Home Device) is an Ancient machine used to control a Stargate. DHDs are pedestal-shaped with a round inclined control panel on top consisting of two concentric circles of "keys" and a translucent red (Milky Way) or blue (Pegasus) hemisphere in the center; the 38 or 36 keys represent the corresponding symbols (or glyphs) on the rim of the Stargate with the central hemisphere serving to engage the stargate. When a DHD is present the gate will not simply activate even if the inner ring is spun in the correct combination as show in the Stargate film. This likely serves as a fail safe to ensure that the correct address was entered. It also serves to allow for "quick dialing" which allows the gate to activate without waiting for the inner ring to spin. power backup When electricity had been away. The DHD also provides power for the Stargate and appears to have a complex programming interface with it that is not normally needed by the operator.

It appears that originally every Stargate had its own DHD, located directly in front of the Stargate and facing it. However, over time some DHDs have been damaged or lost. This presents a difficulty for Stargate travellers, as it is still possible to dial in to a Stargate that lacks a DHD but dialling out again is much more difficult.